This invention relates to internal combustion engines and more particularly to so-called jet or torch ignition engines having a main combustion chamber in which lean air-fuel mixtures are ignited by flame jets caused by combustion of rich air-fuel mixtures in a connecting prechamber or auxiliary ignition chamber that forms a relatively small percentage (i.e. less than 10 percent) of the total clearance volume.
It is known in the art to provide a jet ignition engine with supplemental fuel injection means for supplying fuel directly to the auxiliary ignition chambers to mix with lean air-fuel mixtures admitted from connecting main chambers, thus forming rich mixtures easily ignitable by a spark plug. It has been further suggested that optimum ignition of lean mixtures in the main combustion chambers is obtained when prechamber air-fuel ratios are maintained within a range of from about 8:1 to 12:1 at the time of ignition.